Printed indicia for applying to items of clothing, such as T-shirts, sweatshirts, golf shirts, shorts, hats, and the like, as well as other cloth and paper goods, such as banners, posters, bags, flags, and the like, have become very popular over the last 30 years. Boutiques specializing in printing fanciful and textual indicia such as slogans, college names, sports team names and logos, licensed characters, and the like, on these various media, are commonly seen in stores across the country. The indicia available at these stores can be pre-printed on a substrate and applied with a heated press by operators at such boutiques to any of the aforementioned items purchased by a consumer, or they can be screen printed directly onto the items for later purchase.
In the screen printing process, a stencil screen is typically blocked (called “masked” in the industry) to embody the desired indicia and then placed over the item to be printed. A material, e.g., ink, of one color is then added to the screen surface and flooded onto the indicia by a flood bar of conventional design. The ink may be of any type well-known in the industry for screen printing. After the ink is flooded onto the screen, the ink is squeegeed through the screen interstices onto the item, leaving ink of the desired color where the interstices in the screen are unblocked. The squeegee can be of any type known in the art. Each color is applied separately through screen printing. At times during the printing process the article is also cured or dried through conventional and well known means to set the ink and prevent smearing etc. After printing is completed on the item, the item printed upon is typically moved to a dryer or the like to permanently set the ink onto the substrate or textile.
Assignee of the present invention, M&R Printing Equipment, Inc., Glen Ellyn, Ill., makes several successful textile and graphics printing presses, such as the PROCESSOR®, the RENEGADE™, the PATRIOT®, the ECLIPSE™, the SATURN™, the ADVANTAGE™, the CONQUEST™, the CHALLENGER®, the GAUNTLET®, the SPORTSMAN™, the TERMINATOR™, the ULTIMATE®, the PREDATOR®, the CHAMELEON®, the PREMIERE™, the TRANSFER PRESS™, the BELTPRINTER™, and the PERFORMER™, screen printing systems.
As to particulars, a screen printing machine has at least one station for each color employed. For example, a design incorporating two colors will have at least two printing stations, one for each color. A design employing eight colors will have at least eight stations. Each station generally includes a printing head, which supports a single screen, the specific ink to be used at that station, and a mechanism for applying the ink to the textile. Only one color is employed at each station. The machine will frequently employ one or more setting devices, e.g., flash curing unit, heater, dryer, etc., to cure or set the ink. Specifically, a curing unit is frequently disposed between each printing head so that the textile being printed upon is cured immediately upon printing and before the next color is printed on the first color. For this reason, curing units are made to replace printing heads at the stations. Thus, a machine having 8 stations may have 4 printing head stations and 4 curing stations, with each curing station being disposed between printing stations.
Generally, the substrate to be printed upon travels from station (printing or curing) to station (printing or curing) by one of a number of methods, such as a chain (oval machine) or a rigid arm (carousel/turret machine). In some less expensive models, printing heads are brought to the textile being printed upon.
There are generally three types of machines, that being in-line, rotary—often called a carousel or turret—and oval. In a carousel machine, the stations (with either a printing head or a flash curing unit) are supported on spoking spider arms. The textiles to be printed upon are supported on pallets. These pallets are supported by a separate set of spoking spider arms usually situated below the spider arms supporting the printing heads or curing units. The spider arms carrying the pallets rotate and stop under each station. After stopping, the pallets are brought proximate the printing head or curing unit and printed upon or flash cured. Thereafter, the spider arms supporting the pallets are rotated to the next station.
In an in-line or oval machine, a chain drives the pallet supporting the textile or graphics from station to station. At each station, a printing head or curing unit engages the textile or graphics and prints or cures the material upon the textile or graphics.
In each of the above machines, space or areas are provided (between the spider arms of the turret machine or along a part of the oval track of the oval machine) to load and unload the textiles or graphics onto or from the pallets.
Numerous inks are available in the industry from many different producers. Such inks include water base, sublimation, and plastisol. The ink is cured or gelled on the textile, graphic, or substrate to a critical temperature. The temperature during the curing process must be kept within a window suitable for the ink-setting conditions, typically between 125° F. to 450° F. Unfortunately, with some inks and/or textiles, temperatures are crucial. The quality, color and lifetime of a product may be negatively affected by incorrect temperatures and curing or flash times. For example, with plastisols, the temperature must reach 320° F. However, in a range (below 320° F. or above 350° F.), the plastisol will not properly set, resulting in cracking, or it may become liquified. For example, if the temperature is too low, the plastisol will not cure properly, and will not adhere to the textile/substrate; if the temperature exceeds 350° F., the plastisol will over-gel. Similarly, if a dye in the textile is overheated, it will migrate. Dye sublimation occurs if a textile printed upon is over heated, or “over flashed,” resulting in the dyes of the textile sublimating into the ink. Finally, the textile or substrate being printed upon may scorch or burn, thereby ruining the product and increasing waste and production costs.
In addition to the above, the color set onto the textile will be greatly affected by both the temperatures and the flash or curing time. Clearly, the curing process and machinery are integral to ensure the quality of printed pattern. As such, there are various operating parameters that must be monitored and controlled.
Today's printing processes utilize multiple devices and sensors to facilitate the printing and screening steps and to ensure high quality results. Detailed planning is required to coordinate and integrate the various devices into a reliable manufacturing process.
Several important steps, e.g., sub-processes, in the overall printing process are, or should be, monitored to ensure high quality printing on textiles and graphics. One such integral sub-process involves the aforementioned setting of the deposited ink. It is important to closely monitor the operating parameter, e.g., temperature, power intensity, etc., associated with the apparatus used for setting the ink to ensure proper curing of the printed material. Essential to the curing process is the amount of power supplied to the elements of the setting apparatus or unit. Curing equipment commonly used lacks the precision required to effectively adapt the setting parameters and the device's elements, e.g., quartz bulbs, to the full range of temperatures necessary for proper curing.
Thus, a need exists in the screen printing industry for a control process having the capability to provide precise levels of power to the setting device used during curing of the printed material. In addition, centrally controlling the various sub-processes will significantly improve the quality of the overall printing process.
The present invention is provided to solve these and other problems and to improve upon existing presses and processes.